There are several bandwidth monitor programs for Windows, like the popular DUMeter. NetLimiter does not only what it says (you can cap the bandwidth that different programs are allowed to use) but also keeps track of upload/download numbers for each program. Those are both shareware programs, so you might want to consider using a free program like Down2Home. Unfortunately its meters seem to go crazy when your upload or download is some 2 GB / a day and/or when you've got long uptimes... But if these aren't a problem then it's a good program.